Conventional resilient floor coverings are typically produced in the form of a continuous sheet or in the form of a tile. Resilient sheet flooring typically comprises a bottom, thermally stable base or matte layer coated with one or more layers of similarly formulated polymeric compounds. For aesthetic purposes, an ink layer is also typically disposed between the polymeric layers and the polymeric layers may optionally be chemically or mechanically embossed. Similarly, resilient tile flooring is typically formed as a composite laminated structure having a base layer, a decorative layer applied on top of the base layer, a protective film layer disposed on top of the decorative layer, and a top coat disposed on top of the protective film layer. For aesthetic purposes, the tile may also be mechanically embossed to impart a desired surface texture or pattern.
Currently, conventional resilient sheet and tile floorings both utilize vinyl polymers, such as polyvinyl chloride plastisols, polyvinylchloride homopolymers, and polyvinylchloride acetate resin, as a primary component in the various base and composite layers described above. However, these conventional vinyl flooring systems have several known drawbacks. For example, the long term appearance of an installed resilient floor is dependent on its dimensional stability which refers to the ability of the tile or sheet to retain its original dimension and resist shrinkage over the usable service life of the flooring. To that end, conventional vinyl polymers are incapable of providing the necessary dimensional stability needed to preserve an acceptable long term appearance and service life of an installed resilient floor. In an effort to improve dimensional stability, various chemical stabilizers and fiber based additives including synthetic fibers, fillers, binders, resin, and glass have been incorporated into these polymer systems. Unfortunately however, these additives and stabilizers also result in an increased cost of the end product. Additionally, vinyl polymers are also known to have limited flexural and impact resistance properties as the concentration of additives, such as fillers and fibers, is increased. This is particularly problematic as increasing filler concentration not only increases dimensional stability but is also a recognized means for enhancing fire suppression, thermal insulation, and sound dampening properties of the floor covering as well.
Still further, the installation of resilient flooring typically requires the use of an adhesive material for securing the floor covering to the underlying subfloor structure. Many conventional commercially available adhesive materials are chemically incompatible with vinyl polymers and will in some instances not provide the necessary adhesion. In even more extreme cases, certain adhesives will chemically react with the vinyl polymers resulting in a complete degradation of the resilient flooring. Thus, it has become necessary to provide specially formulated adhesive materials that are chemically compatible with conventional vinyl resilient floor coverings. Understandably, this too creates added installation expenses that would be desirable to avoid.
Resilient flooring also has a limited lifespan and must eventually be replaced, with the resultant used flooring generally being sent to landfill. The vast quantities of flooring waste that are generated annually are burdensome to landfill capacity and have a negative impact on the environment. To reduce the impact of used resilient flooring on the environment, and to reclaim some of the financial loss due to discarding of useful material waste, resilient flooring recycling would appear to be a logical solution. However, the presence of vinyl polymers in resilient floorings creates added complexity for recycling efforts. In particular, vinyl polymers must first be mechanically separated from the myriad of dissimilar polymeric and inorganic materials that are commonly present in resilient flooring. Additionally, the cost of regrinding and re-compounding these resins are generally prohibitive when compared to the significantly lower cost of virgin vinyl resins.
Lastly, and perhaps most importantly, there are significant public health and safety concerns associated with the use of vinyl polymer systems in resilient floor covering systems. As noted above, vinyl flooring products often contain additional chemicals to change the chemical or physical properties of the product. For example, phthalate plasticizers have traditionally been added to make PVC systems more flexible. There are concerns that these additives can leach out of the vinyl products over time. Additionally, there are concerns that vinyl flooring can over time release harmful chemical gases into the air. Some studies indicate that this outgassing may contribute to health complications. In view of these concerns, certain jurisdictions are now considering legislation that would ban the use of certain vinyl polymers, such as PVC, in various consumer goods due to the threats it poses to human and environmental health.
In view of these drawbacks, some in the flooring industry have begun seeking suitable replacements for conventional vinyl systems in the manufacture of resilient floor coverings. One alternative is the use of ordinary thermoplastic polyolefins.
Various methods are available for applying polyolefin backing materials, including powder coating, hot melt application and extruded film or sheet lamination. However, using ordinary polyolefins can also present difficulties. For example, ordinary polyolefin resins possess inadequate adhesion for use in resilient flooring construction. Additionally, ordinary polyolefins have relatively high application viscosities and relatively high thermal requirements. That is, ordinary thermoplastic polyolefins are characterized by relatively high melt viscosities and high recrystallization or solidification temperatures. Even ordinary elastomeric polyolefins, i.e. polyolefins having low crystallinities, generally have relatively high viscosities and relatively high recrystallization temperatures.
One method for overcoming the viscosity and recrystallization deficiencies of ordinary polyolefins is to formulate the polyolefin resin as a hot melt which usually involves formulating low molecular weight polyolefins with waxes, tackifiers, various flow modifiers and/or other elastomeric materials. Unfortunately, hot melt systems can require considerable formulating and yet often yield inadequate delamination strengths. However, the most significant deficiency of typical hot melt system is their melt strengths which are generally too low to permit application by a direct extrusion coating technique. As such, polyolefin hot melt systems are typically applied by relatively slow, less efficient techniques such as by the use of heated doctor blades or rotating melt transfer rollers.
While unformulated high pressure low density polyethylene (LDPE) can be applied by a conventional extrusion coating technique, LDPE resins typically have poor flexibility which can result in excessive stiffness. Conversely, those ordinary polyolefins that have improved flexibility, such as ultra low density polyethylene (ULDPE) and ethylene/propylene interpolymers, still do not possess sufficient flexibility, have excessively low melt strengths and/or tend to draw resonate during extrusion coating. To overcome extrusion coating difficulties, ordinary polyolefins with sufficient flexibility can be applied by lamination techniques; however, lamination techniques are typically expensive and can result in extended production rates relative to direct extrusion coating techniques.
There remains a need for resilient floor coverings that do not contain vinyl polymers. In other words, it would be desirable to provide a non-vinyl resilient floor covering that can be manufactured in a manner and with equipment similar to that used to manufacture conventional vinyl resilient flooring. There similarly remains a need for a non-vinyl resilient flooring that provides dimensional stability and adequate flexural and impact resistance properties, irrespective of the concentration of inorganic filler that may be present. Still further, there is a need for non-vinyl resilient flooring capable of being recycled with greater ease than conventional vinyl flooring products. Lastly, there is also a need for a non-vinyl resilient flooring that is regarded as safe without any associated health and public safety concerns for the environment.